1. Field of the Invention
The present invention relates to a clamping mechanism for a cutting insert for clamping the cutting insert in an insert mounting seat of a holder to detachably mount the cutting insert, in an insert detachable tool used for, for example, grooving or cutting-off of work material.
2. Description of the Related Art
As such a clamping mechanism for a cutting insert used for grooving or cutting-off, the following clamping mechanism is known. In the clamping mechanism, a pair of jaws is formed at a tip of a holder so as to be opened to the tip, and a portion between the jaws is used as an insert mounting seat. A cutting insert is inserted into the insert mounting seat and is sandwiched by both of the jaws, whereby a pair of contacting surfaces of these jaws facing each other comes in contact with a pair of contact surfaces of the cutting insert, respectively, to clamp the cutting insert. Furthermore, for example, the following technology is proposed in PCT Japanese Translation Patent Publication No. 2001-517556. In the technology, the contacting surfaces and the contact surfaces are engaged with each other by male and female means, which are formed in a V-shape to be concave and convex. Each of the male and female means is composed of two flat contacting surfaces extending to have an obtuse angle therebetween. In addition, another technology is proposed in a specification of Austrian Patent Publication No. 006939U1. According to the another technology, in the male and female means formed in a V-shape, two contacting surfaces composing the convex V-shaped male means are formed in a concave shape, and two contacting surfaces composing the concave V-shaped female means are formed in a convex shape having a curvature radius smaller than that of the concave shape so that the contacting surfaces are engaged with the contact surfaces.
However, as described in PCT Japanese Translation Patent Publication No. 2001-517556, in the technology in which the contacting surfaces and the contact surfaces are engaged with each other by male and female means, which are formed in a V-shape to be convex and concave and are composed of two flat contacting surfaces, respectively, the V-shaped angles of both the insert and the insert mounting seat should be formed to be exactly equal to each other. Otherwise, it is not possible to clamp the insert by close contact between the contacting surfaces and the contact surfaces. That is, for example, when the convex V-shaped angle is slightly larger than the concave V-shaped angle, the contacting surfaces just come in line contact with each other at both ends in the width direction of these surfaces orthogonal to the contacting direction. In contrast, when the concave V-shaped angle is slightly larger than the convex V-shaped angle, the contact surfaces come in contact with each other at the inside in the width direction. As a result, the cutting insert is unstably mounted in all of the cases. Furthermore, when there is any error in the angles, contacting positions are varied by the plus and minus of the angles at the outer and inner ends of the contacting surfaces and the contact surfaces in the width direction. Accordingly, for example, when the cutting insert is replaced, if there are plus and minus errors caused by the variation of the shape accuracy between before and after the replacement of the cutting insert, the contacting positions are varied at both ends in the width direction. For this reason, there is a fear that the cutting accuracy will be also varied by the replacement of the cutting insert.
In addition, as disclosed in the specification of Austrian Patent Publication No. 006939U1, in the technology in which the contacting surfaces and the contact surfaces formed in a V-shaped to be convex and concave are formed by two contacting surfaces forming the convex shape and two contacting surfaces forming the concave shape, respectively, after the concave and convex V-shaped angles formed by the contacting surfaces and the contact surfaces are set as to predetermined angles, a total of four concave and convex surfaces are more difficult to be formed so as to have high accurate predetermined curvature radius. Accordingly, when there are errors in the V-shaped angles, there is a fear that the contacting positions between the contacting surfaces and the contact surfaces will be shifted in the width direction. Meanwhile, if the curvature radius of the convex surface is larger than that of the concave surface due to, for example, shape errors, there is a possibility that the contacting surfaces and the contact surfaces come in contact with each other at two inside positions and at two outside positions in the width direction, that is, at a total of four positions. Therefore, the contacting surfaces and the contact surfaces actually come in contact with each other at two positions, which make it impossible to stably clamp the insert. In addition, there is a fear that the cutting insert will deviate and move due to the fact that each of convex-shaped contacting surfaces is guided by a concave-shape contacting surface during the clamping and the cutting.